Barking scraper blades and mountings therefor



Aug. 13, 1957 "r. w. NICHOLSON 2,802,496

BARKING SCRAPER BLADES AND MOUNTINGS THEREFOR Original Filed Feb. 7, 1950 5 Shee'ts-Sheat 1 INVENTOR. THOMAS W N/C'HOLSOV A TJ'OP/WFVS' Aug. 13, 1957 T. w. NICHOLSON 2,302,496

BARKING SCRAPER BLADES AND MOUNTINGS THEREFOR Original FiledFeb. 7, 1950 5 Sheets-Sheet 2 INVENTOR. THOMAS W iV/Cl/Ql 5'0/V BY WM 2. W

A r roe/v5 v5 3 Sheets-Sheet 5 Aug. 13, 1957 'r. w. NICHOLSON BARKING SCRAPER BLADES AND MOUNTINGS THEREFOR Original Filed Feb. 7, 1950 A TTOE/WEVS' United States Patent Ofice BARKING SCRAPER BLADES AND MOUNTINGS THEREFOR Thomas W. Nicholson, Seattle, Wash.

Original application February 7, 1950, Serial No. 144,676, now Patent No. 2,688,349, dated September 7, 1954. Divided and this application August 27, 1954, Serial No. 452,549

Claims. (Cl. 144-208) The present invention relates to the braking element of a mechanical barking machine and especially to a scraper blade type of barking element and its mounting structure. This application is a division of my application Serial No. 144,676, filed February 7, 1950, now Patent No. 2,688,349, dated Sept. 7, 1954, for Log Barking Machine of Light Frame and Having Safety Means for Holding the Log and is related generally to my application Serial No. 407,361, filed February 1, 1954, for Swiveled Scraper Plate Rotary Ring Log Barker.

It is an object to provide a mounting for a barking scraper blade by which such blade is pivotally mounted so that it is angularly movable longitudinally of the log and can be held resiliently against wood of the log so as to scrape bark ahead of it from the wood of the log during relative rotation of the log and the scraper blade.

In preparing logs for the manufacture of veneer and for the manufacture of pulp it is desirable that the bark be removed from the log, which bark may vary in thickness up to two inches, four inches, or even more.

In some mechanical barking machines used heretofore clifi'lculty has been encounted due to the digging in" of the knife used to cut the bark from the log, resulting in jamming of the machine and often consequent damage to expensive components of the machine. Another primary object of the present invention is to mount the scraper blade so as to minimize the danger of such digging in and to mount the scraper blade so that without such tendency to dig into the wood of the log, it will nevertheless elfectively remove from the wood of the log in clean fashion bark even as thick as mentioned above.

A further difficulty heretofore encountered in the operation of mechanical barking machines has been in the removal of stringy bark," that is, bark containing long fibers which cause adhesion of a long section of bark to the log in resistance to a chiseling type of knife. The scraping type of action performed by my barking blade is much more effective to remove bark of this nature.

Also in mechanical barking devices heretofore employed difficulty has been encountered in removing the bark surrounding knots, depressions and other irregularities in the surface of the log. Utilization of a barking blade of the scraper type tends to remove bark much more effectively from such irregularities without nearly as much tendency to jam the barking machine as where a chisel type of knife is used, and if the resistance of an excrescence becomes excessive, the blade will ride over it instead of becoming jammed against it.

Another primary object of my invention is to resiliently hold the scraper blade against the log with operative pressure of a predetermined magnitude, so that rotational stresses exceeding this magnitude will cause the knife to pivotally yield and thereby prevent jamming of the machine. Preferably this is done with two fluid pressure means, one providing for a forcing back of the pivotally mounted tool arm, and the other providing for pivotal or rotational yielding directly of the knife holding member which is mounted on said tool arm.

2,802,496 Patented Aug. 13, 1957 A particular object of the invention is always to have a trailing planar face of the scraper blade or plate meet the surface of the log at a trailing angle with respect to a diametric plane containing the longitudinal axis of a supported log and the line of contact of the scraper blade, such trailing angle always exceeding degrees; or, as a corollary to provide an acute leading angle between a leading planar face of the blade and the confronting portion of a plane tangent to the log at said line of contact, so that the blade will always have a true scraping action as distinguished from a chiseling action which occurs when the angle between the leading face of the blade and that portion of said tangential plane which confronts it is an obtuse angle. As used in the following description, the leading face of the blade or plate is that toward which the adjacent surface of the log has relative movement and the trailing face of the blade or plate is that away from which the adjacent surface of the log moves relatively, whether the log or the blade is the movable element.

in order to remove a swath of bark of substantial width for every relative revolution of the log and scraper blade, it is an object to utilize a blade having an extent axially of the log several times its extent circumferentially of the log. In order that the bark may be removed cleanly along such a swath, it is an object to pivot the blade in a manner such that it can swing about an axis substantiully perpendicular to the plane of the blade to dispose the log-engaging end of the blade parallel with and hence in uniform contact axially of the log with the surface of the wood which the blade end engages.

A further object is to utilize a scraper type of blade having a blunt end so that no chiseling action can occur, and the wood of the log will not be mutilated by digging into it appreciably. Nevertheless, the corner between the leading face of the blade and the blade end must be sufficiently abrupt to perform an effective scraping opera tion, although such corner should not be sharpened because it does not have a chiseling action.

The above-mentioned general objects of my invention, together with others inherent in the same, are obtained by the scraper blade and its mounting structure illustrated in the following drawings.

Figure 1 is an elevation of blade-mounting structure according to my invention. as incorporated in one type of barking machine.

Figure 2 is an end elevation of the machine illustrated in Figure 1.

Figure 3 is an enlarged plan view of the blade-hoiding member or blade yoke and a scraper blade.

Figure 4 is an enlarged elevation of that portion of the machine shown in Figure 2 which directly supports the blade-holding member or blade yoke.

Figure 5 is a side elevation of the blade yoke or bladeholding member and scraper blade illustrated in Figure 3.

Figure 6 is a view in perspective of a modified form of my invention.

Figure 7 is a fragmentary end elevation. partly in section, of a portion of the machine shown in Figure 6 on an enlarged scale.

As illustrative of one type of barking machine with which my scraper blade and its mounting structure can be used, Figures 1 and 2 show a barking machine incorporating a bed 1 on which pedestals 10 and 11 are supported at opposite ends. Pedestal 10 carries a live center 12, and pedestal 11 carries an idling center 13 engageable with the ends of a log to effect rotation of it about its axis. The live center 12 can be rotated by a suitable drive 14 and is held against axial movement. Idling center 13 may be mounted on a piston rod 15 of a hydraulic or pneumatic cylinder 16, serving to move the center 13 lengthwise to clamp a log between it and the live center 12.

On the base 1 are mounted track members 17 and 18 extending generally parallel to the line between the logsupporting centers 12 and 13. On these track members moves a carriage l9, lengthwise of a log supported by the centers 12 and 13, on which the scraper-blade-mounting structure for engagement with the log is supported. An upright arm 2 is carried by a pivot 20 mounted on spaced brackets on an upper portion of the carriage 19 so that the upper end of such arm can swing toward and away from the line of the log-supporting centers 12 and 13. On a lower portion of the carriage is mounted a reaction bracket 21, and a pressure piston-and-cylinder device is interengaged between the arm 2 and bracket 21, such device including a piston rod 23 connected by a pivot 24 to the arm 2 and a cylinder 25 cooperating with the piston rod and connected to the bracket 21 by a pivot 26. Expansion and contraction of this piston-and-cylinder device will move the swinging end of the arm 2 toward and away from the line of centers 12 and 13, respectively. The carriage may be moved lengthwise of the log by chains 27 and 28 driven by any suitable power mechanism.

A scraper-blade yoke or scraper-blade-holding means 45 pivots on a shaft 46, which is mounted in the swinging end of arm 2. Pivotal movement of the blade yoke 45 on shaft 46 is governed by a piston arm 47 and a cylinder 48, which cylinder may be of either hydraulic or pneumatic operation. Cylinder 48 is pivotally mounted on arm 2 by means of a shaft 49. This construction permits not only the arm 2 to be moved toward and away from a log held by the centers 12 and 13 by actuation of the piston rod 23, but also permits of a supplementary movement of the blade yoke 45 by swinging of the blade yoke 45 relative to the arm 2 by actuation of the pistonand-cylinder mechanism 47, 48, independently of movement of the arm 2.

As shown best in Figures 3, 4 and 5, each barking scraper blade or plate 34 in Figures 2 and 4, or 34 in Figures 3 and 5, has parallel planar faces and one edge portion received in a deep notch 35 in the blade yoke or mounting 45. The blade is held in such notch by a pivot pin 3, the axis of which extends perpendicular to the planar faces of the blade, each of said faces being disposed in a plane parallel to a line joining the logsupporting centers 12 and 13. The end of the blade received in the notch 35 is spaced a limited distance from the bottom of such notch so that the opposite, logengaging end 30 of the blade can swing about the pivot 3 into positions inclined relative to a line joining the log-supporting centers 12 and 13. Such angular movement of the blade 34 is, however, limited by contact of the butt end of such blade with the bottom of the deep groove or slot in the blade-holding member 45. I have found a IS-degree angular movement of the blade about pivot pin 3 to be satisfactory.

In operation of the barking machine a log is hoisted or otherwise conveyed to a position between the logcarrying centers 12 and 13, so that the axis of the log is approximately in registry with a line joining the centers. Fluid under pressure is then admitted to cylinder 16 to drive piston rod lengthwise and force the centers 12 and 13 into the log ends. The live center 12 is then rotated by drive 14 in a counterclockwise direction as seen in Figure 2, so that the surface of a log adjacent to the barking scraper blade 34 will be moving upward toward it. Fluid under pressure may then be supplied to cylinders 25 and 48, as may be required to engage the scraper blade 34 in suitable fashion with the surface of the log to be barked, the carriage 19 at such time being at one end or the other of its travel and adjacent to one end of the log. I have found that better control over the positioning of the blade is afforded if the cylinders 25 and 48 are of the pneumatically operated type.

By proper manipulation of the air supplied to cylinder 48 the angle between each of the planar surfaces of the scraper blade 34 and a tangent to the surface of the log at the location of blade contact with the log can be controlled, because supplemental to the control afforded by cylinder 25 the cylinder 48 also permits movement of the scraper blade 34 toward and away from the surface of the log. The end of piston rod 47 forms a bearing sleeve 51 which surrounds shaft 52, thereby connecting piston rod 47 with the blade-holding member 45 so that such blade-holding member is tilted relative to arm 2 about the axis of shaft 46 by extension or retraction of the piston and cylinder mechanism 47, 48. Moreover, utilization of cylinders 25 and 48 of the pneumatic type rather than of the hydraulic type, because of the greater compressibility of air as compared to liquid, will impart a resiliency to the mounting arm 2 and the yoke 45 as these cylinders hold the scraper blade against the surface of a log being barked.

As is evident from Figure 2, the trailing planar face of scraper blade or plate 34 is at an angle of trail relative to a diametric plane of the log containing three lines, namely, a radius r, the axis of rotation of the log (defined by the line joining the axes of centers 12, and 13) and a line of contact of the log-engaging end of the scraper blade with the log, such angle of trail always exceeding I degrees. To state a corollary relationship, the leading planar face of the blade 34, considering the direction of relative rotation of the log and blade, is always at an acute leading angle a to a tangent t which is perpendicular to the radius r joining the axis of rotation of the log and the line of contact of the blade 34 with the surface of the log, Consequently, the blade is always in a trailing and scraping attitude relative to the log surface, and the size of angle a can be decreased to increase the trailing attitude of the blade by retracting piston rod 47 somewhat into cylinder 48 if desired.

Moreover, because of the ability to adjust the pressure relatively in cylinders 25 and 48, the leading angle of the scraper blade 34 relative to the tangent to the logs surface at its line of contact can be altered when barking logs of different size, so that the acute leading a will be the same in every instance or may be varied to suit the desires of the operator.

The log-engaging end of the scraper blade is of blunt form, as shown in Figures 2, 4 and 5, and such end shape may also be selected or altered to suit the preference of the individual operator. In Figures 2 and 4 a somewhat beveled shape of scraper-blade log-engaging end is shown on the blade 34, and in Figures 3 and 5 such blade end is square on the blade 34. In either case the corner between the leading face of the blade and the blade end adjacent to the log constitutes the portion of the blade which engages the wood of the log while the bark is sheared from the log by the adjacent portion of the leading face of the blade. Even though the blade end is square as shown in Figures 3 and 5, there will always be at least some clearance angle between the end of the blade and the debarked portion of the log surface receding from the leading face of the blade when, as explained above, the blade contacts the logs surface so that the leading angle a between the planar leading face of the blade and a plane tangent to the log surface at the line of blade contact is an acute angle.

The proportion of the barking scraper blade as shown in Figures 3 and S is such that the blade will have adequate strength to shear from the surface of the log a swath of bark of very substantial width. In Figures 3 and 5, for example, the width of the blade, as seen in Figure 3, corresponding to its extent lengthwise of the log, is approximately six times as great as the thickness of the blade, as shown in Figure 5. Since, during the barking operation, the carriage 19 is pulled lengthwise of the log by a chain 27 or 28, the movement of the carriage for each revolution of the log should be approximately equal to the width of the scraper blade 34 or 34, so that the blade follows a spiral path around the log during relative rotation of the log and blade until the blade has traversed and removed the bark from the full length of the log.

During such relative movement of the scraper blade and the log surface, the cylinders 25 and 48 will cooperate to maintain the desired pressure of the scraper blade against the log and the desired angle of the scraper blade relative to the log. The pressure in cylinder 25 will have the greater effect in regulating the pressure as desired, because the movement of the swinging end of the blade mounting arm 2 is principally toward and away from the log, whereas the pressure in cylinder 48 will be most influential in maintaining the desired angle between the scraper blade and the log surface at the line of contact of the blade with the log, as described above. Moreover, pressure of the log-engaging end of the blade against the log will cause the blade to swing automatically about the axis of pivot pin 3 so that the end of the blade will be adjusted to any slope which there may be in a longitudinal element of the log, thus distributing the pressure of the blade uniformly along its extent lengthwise of the log. During relative movement of the log surface and the scraper blade, the log-engaging end of the blade 34 or 34' will tend to follow the surface of the log despite irregularities in such surface because of the angular attitude of the blade relative to the log as discussed above. Resistance to relative movement of the blade and log produced, for example, by a projection from the surface of the log will cause the piston rod 47 to be pressed somewhat into the cylinder 48 so that the leading angle of the blade will decrease and enable the blade to ride over the obstruction while scraping at least most of the bark from it. Thus the blade edge has two adaptations to the sur face of the log, one transversely or generally circumferentially of the log, and one longitudinally thereof.

Applied more specifically to the application of my barking tool to a barking machine such as shown in Figures l, 2 and 4, since the rotation of the log is counterclockwise as shown in Figure 2, that is, the surface of the log is turning upwardly against the end of blade 34 which engages it, any force exerted by the log against such blade in excess of that exerted by the fluid pressure within cylinders 25 and 48 will result in adaptation of the mounting arm 2 or the blade mounting yoke 45, or both. Movement of the arm 2 permits the scraper blade to swing backwardly from the log and tilting of the mounting yoke 45 permits a swinging or rotational adaptation of the blade generally circumferentially of the log. Of course. the fluid pressure within cylinders 25 and 48 may be adjusted to the desired magnitudes, both absolutely and in relation to each other, to atford the type of operation desired. Adjustable relief valves are preferably provided on each cylinder so that if a counteracting force is produced on the mounting arm 2 by pressure of the log on the scraper blade 34 the arm 2 will automatically yield to such pressure, thus eliminating danger of serious injury to the machine. Consequently, I have found that the scraper blade courses along the surface of a log during relative rotation of the log and scraper blade, yielding both laterally and vertically to obstructions on the log which in prior machines would have caused jamming.

By having the pressure cylinder 25 controlling the position of mounting arm 2 and by having the pressure cylinder 48 controlling the position of the blade mounting yoke 45 relative to the mounting arm 2 an advantage is gained from the combination greater than the sum of those components derived from each separately. The coordinated pressures exerted by the combination of the two cylinders results in a more constant contact of the scraper blade 34 or 34' with the surface of the log, although such contact is still of a yielding or resilient character.

In Figures 6 and 7 a modified type of scraper blade supporting member 45 is shown supporting the blade 34. Again, the scraper blade is pivotally mounted on the pin 3 to swing about an axis perpendicular to such blade. The scraper blade mounting 45' in this instance is mounted rigidly on the upper end of an upright mounting arm 2' which is pivotally supported on the translatable carriage 19 by means of the shaft 20. The swingin end of the tool mounting arm 2' is resiliently urged toward the surface of the log to be barked by means of the cylinder 25 and the piston rod 23 secured to the arm by a shaft 24 generally in the same manner as described in connection with the barking machine shown in Figures 1 and 2.

A machine of the type shown in Figures 6 and 7 is most appropriate for barking logs generally of the same size, because no special provision is made for adjustment of the plane of blade 34' relative to mounting arm 2' in order to vary the size of the leading angle a between the scraper blade 34' and the tangent to the surface of the log at the line of contact of the scraper blade with the log. The scraper blade being swingably mounted on the pin 3 relative to the blade mounting 45 can still adjust itself automatically to the lengthwise slope of the lo-gs surface, so that the scraper blade will exert a uniform pressure on the log along its extent lengthwise of the log. Except for the independent adjustability of the blades angular atti tude relative to a tangent to the logs surface at the location of blade contact with the log, the operation of the scraper blade and its mounting structure will be generally the same as that described in connection with the mechanism shown in Figures 1 to 5, inclusive.

I claim as my invention:

l. A log-barking machine comprising log-supporting means, a scraper blade having a substantially angular logengaging edge formed by the convergcance of two substantially planar surfaces toward such edge and elongated lengthwise of a log supported by said log-supporting means, said log-engaging blade edge being straight substantially throughout its length, means operable to effect relative movement between said blade and such log in a direction circumferentially of such log with said log-engaging edge of said blade engaged therewith to scrape bark therefrom, and means supporting said scraper blade with one of such substantially planar converging surfaces forming the leading surface of said scraper blade and disposed generally parallel to the longitudinal axis of such log, but with the angle, between such leading surface of said scraper blade and a tangential plane which is perpendicular to a diametric plane of such log extending to said logengaging edge, being at least as small as a right angle.

2. A log-barking machine comprising log-supporting means, a substantially rectangular scraper plate having a planar leading face disposed in a plane intersecting the surface of a log supported by said log-supporting means and disposed generally parallel to the longitudinal axis of such log for engagement of a straight scraping edge portion of said plate therewith, axle-supporting means, an axle supported by said axle-supporting means, said axle defining a pivot axis extending transversely of said planar leading face of said scraper plate. said pivot axis being disposed substantially in a plane perpendicularly bisecting said straight scraping edge portion, said axle mounting said scraper plate for pivotal movement about said pivot axis, and means operable to effect relative movement between said scraper plate and such log in a direction circumferentially of such log with said scraping portion of said plate engaged therewith to scrape bark therefrom.

3. A log-barking machine comprising log-supporting means, an elongated scraper plate having a planar lead ing face disposed in a plane intersecting the surface of a log supported by said log-supporting means and disposed generally parallel to the longitudinal axis of such log for engagement of a scraping portion of said plate therewith, an arm, pivot means defining an axis substantially parallel to the length of such a log and swingably mounting said arm for movement relative to said log-supporting means, said arm having a recess therein receiving a portion of said scraper plate remote from such scraping portion, an axle in said arm recess, said axle being carried by said arm, defining a pivot axis extending transversely of said planar leading face of said scraper plate and supporting said scraper plate for swinging movement about said pivot axis, and means operable to effect relative movement between said scraper plate and such log in a direction circumferentially of such log with said scraping portion of said plate engaged therewith to scrape bark therefrom.

4. In a log-barking machine, log-supporting means, a tool arm pivotally mounted to swing about an axis generally parallel to the axis of a log supported by said logsupporting means, scraper-blade-mounting means carried by said tool arm and having a deep notch in the side thereof adjacent to said log-supporting means, and a rectangular scraper blade having planar opposite faces and being pivotally mounted in said deep notch to swing about an axis extending transversely of said planar faces, one end portion of said rectangular scraper blade projecting from said notch and having a bark-removing edge engageable with the surface of such log, said planar faces lying in planes extending substantially parallel to the longitudinal axis of such log whereby said bark-removing edge of said blade can swing so as to maintain substantially full-line contact with the surface of a portion of such log tapered lengthwise of the log.

5. In a log-barking machine, a pivotally mounted tool arm, a scraper-blade-holding member pivotally mounted on said tool arm, a scraper blade having a planar leading face and a bark-removing edge and pivotally mounted in said scraper-blade-holding member for swinging movement about an axis transverse to said planar leading face to engage its bark-removing edge with the surface of a log disposed with its longitudinal axis extending substantially parallel to said bark-removing edge and transversely of the blades transverse pivot axis, whereby said bark-removing edge can accommodate itself for fullline contact with the surface of a portion of such log tapered lengthwise of the log, and means connected with said scraper-blade-holding member and operable to swing it. relative to said tool arm for altering the angle between said planar leading face of said blade and a plane tangential to that portion of the surface of such log engaged by said bark-removing edge.

6. In a log-barking machine, a pivotally mounted tool arm, a shaft mounted in said tool arm remote from its pivot. 21 scraperblade-holding member pivotally mounted by said shaft, means reacting from said tool arm and connected with said scraper-blade-holding member, operable to pivot said scraper-blade-holding member relative to said tool arm, and a scraper blade pivotally mounted to swing relative to said scraper-blade-holding member about an axis fixed relative thereto, said scraper blade having a bark-removing edge swingably engageable with the surface of a log having its longitudinal axis extending transversely of the scraper blades fixed pivot axis, whereby said bark-removing edge can maintain substantially fullline contact with the surface of a portion of such log tapered lengthwise of the log.

7. In a log-barking machine, a pivotally mounted tool arm, fluid-pressure means connected with said tool arm whereby said tool arm may be resiliently actuated, a scraper-blade-holding member mounted on said tool arm for swinging about an axis fixed relative to said tool arm, a scraper blade carried by said scraperblade-holding member and. having an end portion projecting therefrom, said end portion having a bark-removing edge engageable with the surface of a log that has its longitudinal axis extending generally parallel to the pivot axis of said scrapcr-hla te-holding member, and means connected between said scraper-blade-holding member and said tool arm and operable to swing said scraper-blade-holding member relative to said tool arm for varying the angle between said scraper blade and a plane tangential to that portion of the surface of such log engaged by said barkremoving edge.

8. In a log-barking machine, a pivotally mounted tool arm, manually controlled fluid-pressure means connected with said tool arm whereby a force applied to said tool arm may be controlled, a barking-tool-holding member pivotally mounted on said tool arm, a barking tool mounted in said barking-toolholding member, and fluidpressure means interengaged between said barking-toolholding member and said tool arm and operable to pivot said barkingtool-holding member relative to said tool arm, and consequently to alter the attitude of said barking tool relative to that portion of the surface of a log engaged thereby.

9. In a log-barking machine, log-supporting means, a tool arm having a pivot mounting one end portion of said arm, said pivot being spaced from said log-supporting means and defining an axis extending parallel to the longitudinal axis of a log supported by said log-supporting means, whereby the opposite end portion of said arm is swingable toward or away from a log carried by said log-supporting means, pneumatic piston-and-cylinder means engaged with said tool arm and operable to swing said opposite end portion thereof about the axis of said pivot. a shaft mounted in said opposite end portion of said tool arm, a scraper-blade holder pivotally mounted by said shaft, pneumatic piston-and-cylinder means interengaged between said tool arm and said scraper-blade holder and operable to pivot said scraper-blade holder relative to said tool arm, and a scraper blade mounted in said scraperblade holder having planar opposite faces disposed substantially parallel to the axis of such log and having an edge movable against the surface of a log carried by said log-supporting means, said scraper-blade edge being resiliently pressed against such log by appropriate operation of either or both of said pneumatic piston-and-cylinder means.

10. in a log-barking machine, log-supporting means, barking-tool-supporting means movable toward and away from a log supported by said log-supporting means, a barking tool blade having an angular scraping edge engageable with the surface of a log supported by said logsupporting means, the extent of said blade lengthwise of such log being at least several times its thickness circumferentially of such log, pivot means supported by said barking-tool-supporting means, defining a pivot axis extending transversely of said blade and mounting said barking tool for tilting movement about said pivot axis to maintain said scraping edge parallel to the surface of such log engaged thereby, and means operable to effect relative movement between said barking tool scraping edge and such log in a direction circumferentially of such log with such scraping edge engaged therewith to scrape bark therefrom.

References Cited in the file of this patent UNITED STATES PATENTS Re. 23,765 Pauley et al Jan. 5, 1954 Re. 23,776 Pauley et al Jan. 26, 1954 871,296 Russell et al. Nov. 19, 1907 1,663,794 Clowes Mar. 27, 1928 2,382,896 Medcofl Aug. 14, 1945 2,477,922 Emery et al. Aug. 2, 1949 2,581,829 Alexander Jan. 8, 1952 FOREIGN PATENTS 436,638 Italy June 14, 1948 

